It is known that in gas turbines a fuel-air mixture is combusted in a combustion chamber, producing a hot gas, which is then used in a turbine unit for producing mechanical energy. In doing so, the hot gas is transferred from a combustion chamber into an annular hot gas passage, in which turbine stator blades which are arranged on the casing, and turbine rotor blades which are arranged on the rotor, bring about the conversion of the flow energy of the hot gas into mechanical energy of the rotor. In the transition region between combustion chamber and annular hot gas passage, there is an encompassing axial gap which is construction-dependent, the gap dimension of which varies on account of the temperature-dependent expansions which occur during operation of the gas turbine, and which gap is protected against the penetration of hot gas by blowing out sealing air. Sealing air is especially blown out in the gap which is formed between the end of the combustion chamber which faces the hot gas passage, and the platforms of stator blades of the first turbine stage, or a component between combustion chamber and stator blade.
This method for blocking the gap by blowing out sealing air negatively affects the efficiency of the gas turbine, and also affects the combustion stability inside the combustion chamber, since the sealing air is extracted from the compressor air which is made available for combustion. Especially as a result of different thermal expansions of the components which are associated with the gap, the resulting gap varies compared with that in the cold state of the gas turbine. This requires significant mass flows of sealing air, since these are designed for the largest possible gap which occurs. If a still larger gap than that calculated occurs, in the worst case an inadequate sealing can occur which leads to a local hot gas penetration or hot gas entry into the gap, which leads to a reduced service life of the components which encompass the gap.